1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer using an electrophotographic method or an electrostatic recording method, more specifically, an image forming apparatus configured to detect an inclination of a charging device relative to a surface of an image carrier.
2. Description of the Related Art
In an image forming apparatus such as a copying machine configured to visualize a latent image formed on a photosensitive member and transfer the latent image to a transfer paper to form an image, surface potentials on a photosensitive drum in a main scanning direction becomes nonuniform due to variation of gaps (inclination of a charging device) between the charging device and the photosensitive drum in the main scanning direction. Therefore, fogging can be generated on, for example, a part of a front side or rear side of the transfer paper in the main scanning direction.
Conventionally, in order to address the aforementioned problem, for example, Japanese Patent Application Laid-Open No. 61-151669 discusses a technology which detects surface potentials on a photosensitive drum and adjusts an inclination angle of a charge wire to a surface of the photosensitive drum in an axis direction of the photosensitive drum based on the detected result to make the surface potentials on the photosensitive drum uniform.
However, a method which detects a plurality of surface potentials with respect to the axis direction of the drum to adjust the inclination, discussed in Japanese Patent Application Laid-Open No. 61-151669, requires a plurality of expensive potential sensors and results in increase of apparatus size or hinders cost reduction.
Japanese Patent Application Laid-Open No. 06-102740 discusses an analog image forming apparatus for copying a white reference original and forming an image of the reference original by irradiating with the original image. If image fogging is generated on an output image, the inclination of a charging device to a photosensitive drum is adjusted.
In other words, the image fogging is used as a toner image for adjusting the inclination of the charging device. However, in the method discussed in Japanese Patent Application Laid-Open No. 06-102740, a region where the toner image for adjustment is developed corresponds to a portion to be exposed by an exposure device.
Since density of the toner image on a recording material varies depending on variation of an exposing light amount from the exposure device, when the exposing light amount is not uniformly emitted from the exposure device, it is difficult to accurately measure a density variation amount caused by the inclination of the charging device. Thus, accurate adjustment of the inclination of the charging device cannot be performed.